1. Technical Field
The present disclosure relates to an electron emitter and an electron emission element.
2. Description of Related Art
Carbon nanotubes (CNTs) produced by means of arc discharge between graphite rods were first discovered and reported in an article by Sumio Iijima, entitled “Helical Microtubules of Graphitic Carbon” (Nature, Vol. 354, Nov. 7, 1991, pp. 56-58). CNTs also feature extremely high electrical conductivity, very small diameters (much less than 100 nanometers), large aspect ratios (i.e. length/diameter ratios greater than 1000), and a tip-surface area near the theoretical limit (the smaller the tip-surface area, the more concentrated the electric field, and the greater the field enhancement factor). These features tend to make CNTs ideal candidates for electron emitters.
A carbon nanotube wire is provided as an electron emitter. The electron emitter includes a carbon nanotube wire and a conductive base. The carbon nanotube wire includes a first end and a second end oriented to the first end. The first end of the carbon nanotube wire is connected to the conductive base. The second end of the carbon nanotube wire extends from a surface of the conductive base along a direction far from the conductive base. A number of electrons can be emitted from the second end of the carbon nanotube wire. However a cross section of the second end of the carbon nanotube wire is a planar because the carbon nanotube wire is formed by cutting a longer carbon nanotube wire. Therefore, the field emission characteristic of the carbon nanotube wire is bad.
What is needed, therefore, is to provide an electron emitter and an electron emission element having improved field emission characteristics.